Pulsed ASL MRI Tagging Pulse Pattern Encoding
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Solution Overview
Problem
Current arterial spin labeling (ASL) MRI techniques face challenges in choosing optimal tagging times, affecting sensitivity, specificity, and quantification of blood flow components, particularly in major vessels versus capillary beds, and struggle with low sensitivity and inefficient data acquisition.
Innovation Solution
The implementation of a pulsed ASL MRI system that uses a tagging pulse pattern encoding/decoding method to define and separate cohorts of flowing nuclei based on their tagging times, allowing for efficient data acquisition and improved signal-to-noise ratio by optimizing tagging parameters and generating images for different cohorts of flowing nuclei.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple tagging times are used to capture different blood flow components, then sensitivity and specificity improve, but data acquisition complexity and time increase
Solution Approach 1:
The patent applies periodic tagging pulses at multiple predetermined times within a single scan to label different cohorts of flowing nuclei. This periodic action enables simultaneous capture of multiple blood flow components (arterial, capillary, venous) without requiring separate scans, thus improving measurement precision while avoiding excessive time loss
Solution Approach 2:
The patent combines multiple tagging operations at different times into a single integrated scan sequence. By merging the acquisition of multiple cohorts' data in one scan rather than performing separate scans, the system achieves high detection accuracy for different blood flow components without proportionally increasing total acquisition time
2Measurement precision
If multiple cohorts of flowing nuclei are tracked separately, then quantification accuracy improves, but device complexity and processing requirements increase
Solution Approach 1:
The patent segments the population of flowing nuclei into distinct cohorts based on their tagging time history. Each cohort is identified by a unique pattern of tagging pulse exposure, allowing separate tracking and quantification of different blood flow components. This segmentation enables precise perfusion measurement while using a systematic approach to manage complexity
Solution Approach 2:
The patent uses changes in tagging parameters (timing, presence/absence of pulses) to encode different cohorts. By varying the tagging pulse pattern parameters systematically, the system can distinguish and quantify multiple cohorts without requiring complex hardware modifications, thus improving measurement precision while controlling device complexity
3Measurement precision
If tagging pulses are applied frequently to improve signal strength, then signal-to-noise ratio improves, but background noise and artifact generation increase
Solution Approach 1:
The patent employs periodic tagging pulses with optimized timing intervals to achieve strong signal generation while maintaining temporal separation between different tagging events. This periodic structure allows the system to accumulate sufficient signal for high SNR while the intervals between pulses prevent excessive background noise buildup and reduce artifact generation
Solution Approach 2:
The patent applies preliminary tagging pulses at predetermined times before image acquisition to label cohorts of flowing nuclei. This preliminary action ensures that the nuclei are properly tagged and tracked before measurement, improving signal strength and SNR while the predetermined timing prevents overlapping effects that would generate background noise and artifacts
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables more efficient exploration of blood flow phenomena, improves detection of perfusion, and enhances the accuracy of perfusion measurements by effectively collecting multiple scans' worth of data in a single scan, reducing background noise and optimizing tagging schedules.
Implementation Method 1
imposed tagging RF pulses effective to invert NMR magnetization for at least some cohorts
Implementation Method 2
acquire NMR signal data in an imaging region downstream from the tagging region
Data Source
AI summary
Magnetic resonance imaging (MRI) produces an image representative of flowing nuclei within a subject. For each of plural MRI data acquisition sequences, a non-contrast pulsed ASL (arterial spin labeling) pre-sequence is applied to flowing nuclei in a tagging region during a tagging period (that occurs prior to MRI data acquisition from a selected downstream image region). The ASL pre-sequence includes plural different elapsed tagging times at which a radio frequency (RF) nuclear magnetic resonant (NMR) nutation tagging pulse occurs or does not occur in accordance with different predetermined patterns for corresponding different data acquisition sequences. Acquired MRI data is decoded in accordance with such predetermined patterns to detect MRI signals emanating from different cohorts of flowing nuclei that have been subjected to different combinations of nutation pulses. Acquired MRI data is used to reconstruct at least one image representing flowing nuclei within the selected image region.